Minnesota has suffered through three significant episodes of  extreme humidity and heat (July 17-18, July 30 - August 1, August 4-8) during the summer of 2001. The summaries below utilize long-term Twin Cities climate data to place the collective statistics describing these events into historical context.

Dewpoint Temperatures

While the temperatures found during these sultry episodes have been warm, the notable climate feature of these spells has been the very high dewpoint temperatures. Dewpoint temperature is a measure of the amount of water vapor in the air. Dewpoint temperatures above 70 degrees F are quite uncomfortable, dewpoints above 75 degrees F are oppressive. As seen in the tables below, the number of hours, and the number of days, where dewpoint temperatures have reached or exceeded 75 degrees is at record-breaking levels in 2001.

The highest dewpoint temperature reported thus far in 2001 at the Twin Cities International Airport is 78 degrees recorded late in evening of August 5. However, automated stations located at various Twin Cities locations have reported dewpoint temperatures in the low 80's during the hot and humid episodes. The all-time high dewpoint temperature record for the Twin Citites International Airport is 81 degrees.  This record was set at 11:00 AM - July 30, 1999.

Also notable in 2001 are the number of long stretches of high dewpoints. When the Twin Cities International Airport dewpoint temperature dropped to 67 degrees at 2:00 AM on the morning of August 2, it ended a stretch of 66 consecutive hours greater than or equal to 70 degrees. The highest dewpoint measured during this time was 77 degrees. This streak fell short of the 69 hour record established August 21-23, 1968, but ranks as the second longest of record since 1945. Hourly dewpoint data are not available for the early 20th century. However, there is evidence that the 1968 record MAY have been matched or exceeded previously. When the Twin Cities International Airport dewpoint temperature dropped to 70 degrees at 6:00 PM July 31, 2001, it ended a stretch of 28 consecutive hours of dewpoints greater than or equal to 74.  This broke the record of 25 consecutive hours of dewpoints greater than or equal to 74 degrees set July 3-4, 1977.

Heat Index

A combination of temperature and dewpoint temperature data is often used to calculate an apparent temperature known as the Heat Index. The highest Heat Index value reported thus far in 2001 at the Twin Cities International Airport is 109 degrees, occurring July 31, August 6, and August 7. The all-time high Heat Index value for the Twin Cities is believed to be 120 degrees on July 11, 1966. Heat index values in excess of 105 degrees are considered to be dangerous.

Air Temperature

As mentioned previously, the preponderance of very high dewpoint temperatures has been the most striking feature of the heat spells. While a handful of daily maximum temperature and high minimum temperature records have been set in 2001, the tables below show that total number of days of very hot summer days in 2001 falls well short of all-time highs.

July and August 2001 daily record temperature event reports for the Twin Cities International Airport (through August 7).

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
300 AM CDT WED AUG 01 2001

...RECORD HIGH MINIMUM MATERIALIZES AT MINNEAPOLIS...
THE LAST DAY OF JULY PROVED TOO MUCH FOR THE OLD RECORD HIGH MINIMUM 
TEMPERATURE...OF 76 DEGREES...SET DURING THE SUMMER OF 1975. THE NEW
AND IMPROVED RECORD MAX LOW READING OF 77 DEGREES WAS RECORDED ON JULY
31ST AT PRECISELY 607 AM.

        
RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
420 PM CDT MON AUG 6 2001
...A NEW RECORD HIGH FOR THE TWIN CITIES...
THE HIGH TEMPERATURE IN THE TWIN CITIES...HIT 99 DEGREES AT 415 PM.

THE IS A NEW RECORD HIGH FOR TODAY.
THE OLD RECORD WAS 97 SET AUGUST 6 1916.

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
850 PM CDT MON AUG 6 2001

...A NEW RECORD...WARM LOW FOR THE TWIN CITIES...
THE LOW TEMPERATURE IN THE TWIN CITIES WAS...80 DEGREES AT 632 AM.
THE IS A NEW RECORD...WARM LOW FOR TODAY.
THE OLD RECORD WAS 76 SET AUGUST 6 1916.

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
310 PM CDT TUE AUG 7 2001
...A NEW RECORD HIGH FOR THE TWIN CITIES...
THE TEMPERATURE IN THE TWIN CITIES...HIT 98 DEGREES AT 300 PM. THIS
IS A NEW RECORD HIGH FOR TODAY. THE OLD RECORD WAS 97 SET AUGUST 7
1949 AND AGAIN IN 1983. 

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
110 PM CDT WED AUG 8 2001

...A NEW RECORD WARM MINIMUM FOR THE TWIN CITIES...
THE TEMPERATURE IN THE TWIN CITIES...FELL TO ONLY 76 DEGREES
AT THE TWIN CITIES AIRPORT BY MIDNIGHT.  THIS IS A NEW RECORD
FOR AUGUST 7TH. THE OLD RECORD WARM LOW WAS 74 SET ON AUGUST 7 
IN THE YEARS 1930 AND 1937.

RECORD EVENT REPORT
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
135 AM CDT THU AUG 9 2001

...A NEW RECORD WARM MINIMUM FOR THE TWIN CITIES...
THE LOW TEMPERATURE IN THE TWIN CITIES YESTERDAY WAS...77.
THIS IS A NEW RECORD FOR AUGUST 8.
 
THE OLD RECORD WARM LOW WAS...75 SET AUGUST 8 1914.